Dry battery and method of making the same



G. W. HEISE INVENTOR.

ATTORNEYS.

Jan. 26, 1932.

DRY BATTERY AND METHOD OF MAKING THE SAME Filed Aug. 31, 1926 PatentedJan. 26, 1932 UNITED STATES PATENT OFFICE GEORGE W. HEISE, OF LAKEWOOD,OHIO, ASSIGINOR TO NATIONAL CARBON (XIMPAN'Y,

. IN 0., A CORPORATION OF NEW YORK Application filed August 31, 1926.Serial No. 132,827.

This invention relates to dry cells and particularly to dry cells of thebag or bobbin type".

The invention has for a principal object the provision of improved meansfor centering the cathode or bobbin electrode with respect to thezinc-cup anode.

It is a further object to eliminate the wrapping customarily used onbobbins to prevent their disintegration during handling and to providean improved armoring coating for the bobbin and a method of forming thesame.

It is a still further object of the invention to improve the shelf lifeand operating efficiency of dry cells by controlling the composition ofthe armoring coating for the bobbin and the composition of theelectrolyte paste.

Other objects are disclosed in the detailed description which follows.

In the manufacture of dry cells of the bag or bobbin type it iscustomary to provide the bobbin, which comprises a mixture ofcarbonaceous material and depolarizer molded around a carbon electrode,with a protective wrapping of gauze, cheese cloth or thelike held inplace by thread or other binding means. This type of cell givessatisfactory results, but the manufacturing costs are high owing to theexpense of thewrapping material and the hand labor required in applyingit to the bobbin. It has also been proposed to dispense with thewrapping entirely, or to form a protective coating upon the bobbin bydipping it into paste or similar material which on being subjected todrying will form a bibulous adherent coating. Such coated bobbins showgood results when used in dry cells but the methods heretofore employedin forming the coating have not been entirely satisfactory. When thebobbin is dipped in paste it is a very inconvenient unit to handle sinceit is sticky and tends to adhere to any surface with which it may comein con- According to the present invention, concurrently with theformation of the bibulous protective coating on the bobbin, a ring ofpaste is formed about the base of the bobbin. This ring serves to spaceand center the bobbin with respect to the zinc cup. The means and methodemployed in forming this ring of paste facilitate the manipulation ofthe wet dipped bobbin and permit of its being placed upon a horizontalsurface for the purpose of drying the coating without danger that thebobbin will adhere thereto.

In the drawings, Fig. I is a perspective view of a partially completedbobbin;

Fig. II shows the bobbin of Fig. I, after the paste coating has draineddown and formed a centering ring about the base of the bobbin, inassembled relation with the other elements of a dry cell; Fig. III showsa bobbin which is associated with a modified form of the means forretaining the fluid paste about the base of the bobbin until it has set.

According to a preferred embodiment of my invention, a bobbin 1 is firstformed by molding moist battery mix comprising manganese dioxide, carbonor graphite, and preferably electrolyte salts, around a carbon rod 2.The molded bobbin is then dipped into a paste composed of water, cornstarch, wheat flour or corn meal, and electrolyte salts. The dippedbobbin is then set on a small square or disk of thin paper 3, forexample tissue paper, and allowed to dry until the paste coating 4 hasbecome firmly set but not long enough to show desiccation. Fig. I showsa freshly square 3. The thin paper sticks to the bobbin but does notbecome sticky on the under side, so that the bobbin may be set on ahorizontal surface without adhering. A portion of the fluid paste whichis carried by the bobbin when it is removed from the dipping bath runsdown the side of the bobbin and collects in a ring 5 at the base. Thispaste ring solidifies on drying and forms an eflicient spacing andcentering means for the bobbin when it is introduced into the 'zinc cup6. The thin paper disk does not itself act as a centering or spacingmember but on the contrary only acts to retain the paste which collectsabout the base of the bobbin so that it can solidify in the form of aring integrally joined to the bobbin. The thin disk should preferablyalso be made of a porous paper which is readily permeable to electrolyteand will therefore interpose very little resistance to the flow ofcurrent between the bobbin or cathode and the bottom of the zinc cupanode,

thus insuring the utilization of the zinc which is contained in thebottom of the zinc-cup anode and thereby increasing the effectiveservice life or capacity of the cell as compared with similar cells inwhich insulating or high resistance spacing and centering means areused.

In some cases it may be desirable to place the dipped bobbins intoshallow, thin paper cups instead of upon plain flat disks or squares.Such cupsser ve to hold the paste mg, serves a use penetration of pasteor electrolyte into the and retain it about the base of the bobbin untilit has hardened suflicientlyto act as a spacing member. Fig. III showssuch a cup 7 into which a freshly dipped bobbin has been placed. Surpluspaste runs down the sides of the bobbin and collects in the cup to formthe ring 8.

i The paste armoring or hardened coating, when care is taken to form itof the proper hardness and toughness without undue-dryul function inpreventing bobbin.

With unprotected bobbins heretofore used such penetration is anoccasional occurrence which may cause a loss in capacity of as high as30-40% on certain types of service. I have found that the best resultsare obtained when the paste coating is allowed to dry only long enoughto set firmly but not long enou h to show desiccation. Ordinarily,drying or 30 minutes at 7 0 7 5 F. in an atmosphere of 50% humidity issatisfactory. If the bobbins are dried for a longer period, especiallyin dry air, the results are unsatisfactory due to the loss of moistureand the formation of high resistance layers at the bobbin surface; Too

short a period is even more unsatisfactory, since the paste layer formedby dipping does not under these conditions protect the bobbin fromelectrolyte penetration while the cell is being assembled. vAcommercially preferable method of setting or toughening the pastecoating consists in drying the dipped bobbins at approximately 175 F.for from 3 to 5 minutes. Still another method consists in dipping a hotbobbin into cold paste. It will be understood that these methods of setting or toughening the paste coating are not limited to use inconjunction with the means for centering the bobbin above described.

It has heretofore been recognized that if, in making up the depolarizermix, electrolyte containing a high concentration of zinc chloride isincorporated therewith, the keeping quality of the cell and itsefiiciency for certain types of service, e. g. radio and flashlightservice, are improved. However, as a practical matter it has beendiflicult to introduce the desired amount of zinc chloride into themix'under factory conditions because of the irritating effect of thezinc chloride on the hands of those engaged in handling the mix. It isnot immediately practicable with ordinary compositions to introducethese high quantities of zinc chloride in the bulk of the paste forvarious reasons, including the rapidity with which the paste would tendto thicken. According to the present invention the advantages of highzinc chloride concentration in the cell are obtained by using a dippingpaste having an abnormally high zinc chloride content and reducing thezinc chloride content of the mix to such limits as to permit of itsbeing handled without trouble, or eliminating zinc chloride from thesolution used in wetting the mix. I prefer that the zinc chloridecontent of the dipping paste shall be as high as is compatible withmanufacture of paste of the desired viscosity. However, the zincchloride content is dependent to some extent on the composition of themix electrolyte. Thus if water only is used in wetting the mix, 35 partsof zinc chloride per 100 parts by weight of water in paste electrolytemay be used; with mix wet with zinc chloride solution a lower concen--'tration, e. g. 28 parts of zinc chloride, is indicated. Improvement ofthe order of 10 to 15 per cent in radio service of miniature cells mayreadily be effected by such precedure. Concentrations ranging from 20 to35 parts of zinc chloride per 100 parts of water have successfully beenused.

According to the preferred embodiment of my invention the dipping pastecontains no mercuric chloride. However, it is preferable tocorrespondingly increase the mercuric chloride content of the pastelayer used to fill the space between the bobbin and the zinccup anode inthe assembled cell so that the cell will contain the amount of mercuryordinarily used. The paste ar'moring for the bobbin tends to reduce thediffusion of mercury from the paste layer into the bobbin, and for thatreason tomaintain more mercury in effective relation tothe zinc anodefor amalgamation therewith without increasing the quantity of mercury inthe cell. The increased mercury concentration of the paste layer alsoimproves the keeping qualities of the cell and therefore prolongs itsshelf life. It is also possible to use paste with normal mercury contentin forming the paste layer between the bobbin and the zinc anode withoutmaterial reduction in the keeping qualities and shelf life of the cell,although the mercury content of the cell thereby has been reduced andmanufacturing costs have been correspondingly reduced.

By following the practice outlined above 29 it is possible to effect theentire or partial elimination of the cooking operation heretoforeconsidered indispensable for the production of cells of good quality,because of the electrolyte penetration previously discussed as withuncooked paste. Cooking may be omitted entirely without danger that thecells will spoil while being stored prior to use, or, to hasten thesetting of the paste, a cooking temperature ordinarily too low to beeffective ao may be utilized. In either case danger of over-cooking isobviated.

I claim: 7 1. Process of encasing the depolarizing mix of a bobbin andforming a means thereon for centering the bobbin in an anode cup,comprising completely coating the sides and bottom of the moldedunwrapped depolarizing mix with an excess of fluid paste; placing thebobbin on a support whereby the exo cess paste is collected in the formof a ring about the base of the bobbin and adhering thereto, andsubjecting the coated bobbin to a regulated drying action to toughen thepaste coating. f

larizing mix of a bobbin and forming a means thereon for centering thebobbin in an anode cup, comprising immersing the unwrapped depolarizin'mix in a cereal paste; collecting 5 an excess 0 paste on the surface ofthe mix;

placing the bobbin on a porous bibulous material upon which the excesspaste is collected in the form of a ring about the base of the bobbinand adhering thereto, and then subjecting the coated bobbinto aregulated drying action to toughen the coating.

3. A dry cell comprising an anode cup; an unwrapped bobbin therein ofsmaller diameter than said cup; a. coating permeable to electrolyte onsaid bobbin; a ring of the same composition as said coating integraltherewith and-formed about the base of said bobbin; said ring extendingto the walls of said cup. 65, 4. A dry cell. comprising an anode cup;

2. Process of encasing the moldeddepo' an unwrapped" bobbin thereinspaced from

